Synchroscope



Sept. 19, 1944 BLOK 2,358,439

SYNCHROSCOP E Filed March 17, 1945 Our/ur MIA/6A? JTHGE Psw sqeiaimAmmlll IlthNetllRlanlc In power apparatus the-incandescent lampprcvidesaneasycmtrivancefortheopticalcontrol .og the synchronization oftwo alternating This invention for its object to provide adevlcebymsansorwhichthesameresult can be obtained in cases where theavailable energy is far too icw for the operation oi' an incandescentlamp. Such cases occur. for example, incalibratingtheaeropointofthediaioi'aiow frequency oscillator, inadmixing carrier wave atthereceivingendoiawireless system.andinmichrcnising ordinaryalternating current powerAccordingtotheinventiomiorthispurpe useismadeofacathode-ray tubeoithekind known as magic eye andintermediste the con; trolelectrods andcathodsoi the said-urbe is arranged an impedance which practically formsa by-psss for any frequencies higher than thatcanstillbeseenbytheeye.

If the diiferencefrequency formed from the two frequencies to besynchronised'l is superimposed cn the control grid of the amplifier tubeincorporated in the magic eye, a constant deflection of the luminousspot willbe observed so long as the difference-frequency exceeds, forexampie. cycles/sec. If, however, this frequency fails to below 20,ilickerings are observed whosespeedisreducedaccordingasthepointofynchronisation is approached. On this'point being reached the luminous image is again fully 'Ihe ampliilertube as med in my invention can be operated linearly and may thereforebe used at any frequencies to impiify diiference-frequency oscillations.This feature is particularly 1mlicsirable in the case at a low-frequencyoscilla- In order that the invention may be clearlyunderstoodandreadilycarriedinto effectitwill now be described more fullywith `reference to thc Mmmm drawing. in which one exampie of applicationof a low-frequency oscillato is diagrammatically shown.

Referring to the single. ngure of the drawing, i and 2 desiganteoscillators which set up the frequencies fr -and fr respectively, atleast one of these frequenciesbeingvariahiethroughamore or less wideregulating range (e. g. 10 kilocycles).Atamixingstagelthesefrequenciesarecollected and thediiference-frequency.- fi-f: is selected. This frequency is appliedbetween the su. sans No. 41am sem-mr n. im

s dem (cl. 11s-us) parto! a "magic eye tube. this part comprising apentode.

The screening grid! of this pentods whose anode is designated I isdirectly connected within thsjtube to the control electrode I of the"eye" proper whose `iiuorescent screen is desig- 4 nated l.

vThe screening grid l islupplicd acrossaresistanceIlandisinadditlonconnectedviaa condenser Il tothe earthed point Ilwhence a resistance' shunted by a large condenser Il v leads to thecathode l.

' The condenser Il has-such a capacity, e. g.

0.1 mfd.. that it, in cooperation with the resistance Il, formsv aby-pass for frequencies above cycles/sec. between the screening grid 0-(and consequently. also the control electrode 8) and earthsothattheconnecticninteraliawiththe high capacity of the condenser Il (forexample 50' mid.) appreciable potential uctuatlons having a frequency ator above'20 cycles cannot arise between the control electrode 8 and thecathode 1l. Elements l and l are, therefore. decoupled with respect tothe cathode l.

The oscillations applied between l and l and having thedifierence-frequency fi-fs, which valuev may vary for examplebetween 0and 10,000

cycles/sec., are amplified hy the pentode and used in known manner, ifnecessary after iurther amplication, for the purpose for 'which they aredesired.

Since the tube V is substantially a dual purpose tube, it muy at timesheconvenient to use its pentode section for amplifying the outputcomponents from the mixer stage l. In the f pentode section, in additionto the common cathode I and the common grid I, an anode 1, a screenVgrid 0 and a suppressor grid 2| are provided. Coupled to the outputcircuit which includes the anode 1 is a following amplier stagecomprising a pentode tube i8, the input circuit of which includesresistors I6 and i1 connected between ground and the control grid. Thiscon-l troll grid is coupled to the output circuit of tube V by means ofa capacitor Il. Tube il has the usual pentode electrodes. and itscathode is connected to ground through a cathode resistor i0.

lThis resistor isrpreferably shunted .by a capacitor 20. In the outputcircuit of tube l5 a load resistor 22 is/provided and, if desired, theoutput circuit may be coupled to a utilization device by means of acapacitor 2l.

In order to calibrate the zero point of the dial fs is caused toapproach fr, or conversely the difcontrol grid l and the cathode l ofthe amplifier es ference-frequency lr-fa is mank and smaller. so im nuns amel-enea u greater than 20 cycles per second variations of theluminous spot are not seen on the screen I because the electrodes l andl are suiilciently decoupled by the condenser' Il for this frequency.

The latter condition is. however,4 changed below 20 cycles/scc. andunder these circumstances the diiference-frequency becomes visible as amore or less slow ickering of the luminous-spot. When the frequency ofthis ilickering falls to zero the twofrequcncies fi and l: are indicatedas exactly equivalent and -the pointer of the to cover the zero point.

I claim: Y

l. A synchroscope comprising a` mixer stag having input circuits uponwhich alternating currents from two separate sources may be irnpressed,an output circuit for said stage, a dis" charge tube having an electrongun and a nuorescent indicating screen, and means including a controlelectrode in said tube coupled to the output circuit of said mixed stageeffective onlyl for producing a perceptible flicker effect whichl is afunction of the ditIerence-frequency resulting from the mixing of saidalternating curmeter of the difference-frequency should beset ammpendent'sourcss ofappscaimatalythesamefrequency the synchronous.relationship between whichistobeindicamavisiualindicatordischarge tubehaving acatbcds, auorescent targetanodeandaeontrolslectrodseilectivetovary the area of iiuorescent response to electronicemisslon in saidtubs, means for causing said tube to-be controlled by output potentialsfrom said mixer stage, and means for cancelling out any-perceptibledicker response in said tuhs which would result 'from a phase rotationof potentials from one of said sources with rpect to the other-,when therate of said phase rotation is at least 2o revolutions per second.

' 4. A system for producing a perceptible flicker response which -isuseful to observe small dif- -iei'ences between the frequencies of twoelectric sources, said system comprising an elec tronic mixed stage onwhich potentials from said sources are 'simultaneously l:..pressed. Va

discharge tube of the type known as a "magic rents when they are causedto approach synchronism, and the difference frequency` is no greaterthan 20 cycles per second.

2. A synchroscope according to claim 1 and including a wave trapconnectedto the input circuit of said tube and adapted to eiectivelybypass frequencies above 20 cycles per second.

3. A synchronism indicator system comprising a mixer stagepmeans forsimultaneously im` pressing two input potentials on said mixer stage,said input potentials being derived from indeeye," said tube comprisinga cathode, a control electrode. and a target anode rendered iluores.-cent Iby means oi a suitably responsive coating thereon, means forapplying output potentials

